Shadow mask support comprising flat, bimetallic element attached to inwardly projecting frame flange

ABSTRACT

Parallax barrier supporting means comprising substantially flat, rectangular bimetallic elements are disclosed. The elements are attached to the upper portion of the barrier frame and have depending springs attached thereto. The springs have apertures formed therein to mate with studs formed on the tube envelope inner wall.

United States Patent Miller [54] SHADOW MASK SUPPORT COMPRISING FLAT,BIMETALLIC ELEMENT ATTACHED TO INWARDLY PROJECTING FRAME FLANGE [72]Inventor: Larry R. Miller, Waynesboro, Pa.

[73] Assignee: Sylvnnia Electric Products Inc.

22 Filed: Au .s,197o

[211 App]. No.: 6l,l 63

521 0.5. CI. ..313/ss s, 313/292, 313/288 511 1m. 01 .1101 29/06, HOlj31/20, 1101, 19/52 531 Field otSearch ..313/85 s, 92 a, 292

1 1 Feb. I, 1972 [56] Relerenoes Clted uumzo STATES PATENTS 3,330,9307/1967 Shrader .313/85 s 3,454,813 7/1969 Lewinson .3l3/85SX 3,524,9738/1970 Rigdon ..3l3/85S Primary Examiner-Robert Sega! AttorneyNorman J.O'Malley, Donald R. Castle and William H. McNeill 57] ABSTRACT Parallaxbarrier supporting means comprising substantially flat, rectangularbimetallic elements are disclosed. The elements are attached to theupper portion of the barrier frame and have depending springs attachedthereto. The springs have apertures formed therein to mate with studsformed on the tube envelope inner wall.

PATENTEDFEB 1:972 3 7 3339793 sum 10F 3 I INVENTOR. LARRY R. MILLERATTORNEY PATENTED FEB 1 1972 SHEET 2 BF 3 INVENTOR. LARRY R. MILLER PM w' ATTORNEY SHADOW MASK SUPPORT COMPRISING FLAT. 'BIMETALLIC ELEMENTATTACHED TO INWARDLY PROJECTING FRAME FLANGE BACKGROUND OF THE INVENTIONThis invention relates to color cathode-ray tubes and more particularlytotemperature compensating supporting systems for the parallax barriermounted therein.

In conventional color cathode-ray tubes in use today a mosaic,cathodoluminescent phosphor screen is formed on the interior surface ofthe viewing screen. Positioned at a point remote therefrom is anelectron source formedto provide an electron beam or beams for excitingthe phosphors to luminescence. Intermediate the electron source andscreen,but closely adjacent to the screen, is provided a parallaxbarrier to aid in color selection. In the color tube in greatest use,the parallax barrier acts as a shadowmask and comprises arelativelyfragile foraminated portion attached to a relatively rigidframe. Support means, generally in the form of apertured leaf springs,are attached to'the sides of the frame and cooperate with studs formedon an inner surface of the tube wall. The apertures in the foraminatedportion are particularly aligned with the mosaic pattern of the screenand for successful maintenance of color purityv it is necessary thatthis alignment remain relatively constant during tube operation. Thiscondition has been difficult to maintain in the past because of the heatgenerated at the parallax barrier due to the bombardment thereon of theelectron beam or beams. Misalignment occurred because of the differencesin thermal expansion of the thin material in the foraminated portion andthe heavier material in the frame. This differential in expansion duringtube operation caused the foraminated portion to bow toward the screenthus disturbing the alignment.

To correct this problem, a recent innovation provides for intermediatemounting members between the frame and the supporting springs whichcomprise bimetallic elements having upper and lower portions connectedby an expansion hinge. The lower portion is affixed to the frame and theupper portion has one end of a leaf spring attached thereto in such amanner that the free end of the spring. engages a mating tapered studwhich projects inwardly from an upstanding wall the screen andthe end ofthe wallremote from the foraminous portion has formed thereon aninwardly projecting flange. The

mounting means comprises a plurality of substantially flat metallicelements positioned at spaced intervals about the frame and attached tothe flange. Each of the elements has a depending spring which extendstoward the screen between the circumferential wall of the frame and theenvelope. The springs have-means formed therein for engaging matingmeans formed on the envelope.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an elevational sectionalview of a typical color cathode-ray tube, greatly simplified;

FIG. 2 is a perspective view-of the mounting means;

H6. 3 is a sectional plan view of thefaceplate portion of a colorcathode-ray tube utilizing the invention;

HO. 4 is a sectional 'plan view similar'to FIG. 3 showing an alternateembodiment of the invention;

FIG. 5 is a sectional elevational view taken along the line 5-5 of FIG.4;

FIG. 6 is a plan view taken along the line 6-6 of FIG. 5;

FIG. 7 is a plan view similar to FIG. 6 but illustrating the element ofFIG. 2; and

FIG. '8 is a partial, sectional elevational view showing an alternatemounting embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding ofthe present invention, together with other and further objects,advantages, and capabilities thereof, reference is made to the followingdisclosure and appended claims in connection with the above-described ofthe faceplate. In designs of this type the expanding hinge or loopprojects inwardly toward the center of the tube and thus somemodification of the frame isnecessary to accept this projecting hinge.

Another innovation involved a similar intermediate mounting memberutilizing a contracting or closing loop or hinge. In this type ofstructure the loop'projected away from the frame and occupied the areabetween the frame and the faceplate sidewall, thus obviating anymodification to the frame. This type, however, presents problems insmaller screen sizes of color tubes where the space between the frameand sidewall is apt to be critical.

OBJECTS AND SUMMARY OF THE INVENTION Therefore, it is an object of thisinvention to enhance color television tube operation.

It is another object of the invention to obviate the difficultiesinherent in the prior art structures.

It is another object of the invention to provide atemperature-compensating mounting means which is simple and inexpensiveto manufacture and install.

These objects are accomplished in one aspect of the invention by theprovision of a color cathode-ray tube containing, within an evacuatedenvelope, a mosaic cathodoluminescent screen, an electron sourcepositioned remote from said screen, a parallax barrier mounted betweenthe source and the screen but closer to the screen, and mounting meansfor releasably mounting the barrier within the tube. The barrier iscomprised of a foraminated relatively fragile'portion whichis attachedat its peripheral edge to one end of a circumferential sidewall of arelatively rigid frame. The circumferential sidewall of the frameextends substantially perpendicular to drawings.

Referring now to the drawings with greater particularity, there is shownin FIG. I a simplified view of a typical color cathode-ray tube 10having an evacuated envelope 12. A faceplate portion I4 seals one end ofenvelope l2 and a reduced diameter neck I6 seals the other end. Anelectron gun I8 is positioned within the neck for directing one or morebeams of electrons to a mosaic phosphor screen 20 which if formed onthe. interior surface 22 of faceplate 14. A parallax barrier 24, to aidin color selection, is removablymounted adjacent the phosphor screen 20.

The parallax barrier, which in this instance is a shadow mask, comprisesa relatively fragile-foraminated portion 26 attached at its peripheraledge 28 to one end of a circumferential sidewall 30 of a relativelyrigid frame 32. The sidewall 30 extends substantially perpendicular tothe screen 20 and is parallel to an upstanding circumferential wall 34of envelope I2 which projects from faceplate 14. The end of wall 30remote from the foraminated portion 26 is provided with an inwardlyprojecting flange 36.

The novel-mounting means 38 of this invention is shown isolated in FIG.2 and comprises a substantially flat bimetallic element 40 comprised oftwo-contiguous layers 42 and 44 having different thermal coeflicients ofexpansion. Layer 44 has the higher coefficient of expansion and can be,for example, a composition of 22% Ni, 3% Cr, with the balance Fe. Layer42 has a lower coeflicient of expansion which should be substantiallyzero over the temperature range of normal tube operation (22-7-5 C. atthe mask) and can be, for example, Invar, which has composition of 36%Ni and the balance Fe. Such a material is available as Chace No. 2400bimetal from the W. M. Chace Co. Element 40 is substantially rectangularand has short edges 46, 48; a long front edge 50 and a long back edge52; and upper and lower surfaces 54, S6. A depending spring 58 isattached to element 40 and, as is shown in FIG. 2, the attachment isaccomplished via a spring flange 60 fixed to upper surface 54 as bywelding. This is an exemplary attachment only, and the spring flange canbe attached to lower surface 56 or the spring can be formed without theflange and 64 for engaging a projecting stud 66, a plurality of whichare positioned in wall 34 of tube 10.

The mounting means 38 of this invention can be utilized in either of thetwo most prevalent supporting systems currently in use, namely: a threepoint system and a four point system. Each of these systems will bediscussed in turn.

in the three point system, as illustrated in H6. 3, a first mountingmeans 38 is positioned substantially on the vertical axis of the tube10. Bimetallic element 40 is fixedly attached to flange 36 of frame 32with the high-expansion material lowermost and adjacent the flange 36.Attachment is made at a plurality of points, indicated as xs in thedrawing, and the attaching means can be any suitable type, such aswelds. For the first mounting means 38, the welds are all positioned asubstantially equal distance in from back edge 52.

The remaining two-mounting means 38 are positioned opposite one anotheron the short sides of frame 32, some distance below the horizontal axisof tube 10. ldeally, they are about 1 l from the mounting means locatedon the vertical axis. The mounting means on the short sides of the frameare identical to the first-mentioned means on the vertical axis of tubeexcept that the attachment points thereon are spaced progressivelyfurther from the back edge 52 of the elements 40 as the distance fromthe horizontal axis increases. This reduces the active length of thebimetal and compensates for the fact that the side mounted elements arenot on the horizontal axis.

The four point suspension system is shown in FIG. 4 and comprisesfour-mounting means 38, two being mounted substantially on the verticalaxis and two being mounted on the horizontal axis. With this type ofequalized support, all of the individual attachment means for theelements 40 are equally spaced from the back edge 52.

During operation of the tube heat generated in the mask and frame bybombardment of the electron beam or beams thereon causes the mask 26 toexpand. Without some form of compensation, the expansion destroys thecritical alignment between the holes in the mask and the mosaic phosphorscreen, resulting in a loss of purity. With the mounting means of thisinvention, however, this heat-generated distortion is corrected as isshown in FIG. 5. As the heat builds up in the mask and frame it istransferred to the bimetallic element 40 which bends as shown because ofthe differential in thermal expansion between the layers. Since onepoint of the system, namely the spring aperture and the fixed stud 66 iscompletely stationary, this bending movement of the bimetal istransferred into downward movement of the mask and frame, which servesto maintain alignment.

An alternate embodiment ol'the invention is shown in FIG. N. "cu-in,tlnflange 36 is provided, at least at those areas when-at elements 40are to be connected. will! a raised protnlitltllltt or rib Ml. 'l'hisinsures that the bimetal is not being pressed against the frame. sayfrom heat-caused distortion during welding. if the bimetal were beingpressed against the frame then the first say, of heat, might serve onlyto relieve the tension the bimetal was originally in. In such instance,the degree of movement obtainable might not be sufficient to correctcompletely for the misalignment occuring during tube operation.

While various types of bimetallic elements can be used, excellentresults have been achieved using Chace Type 2400. The element 40 isapproximately l.5 inches long and 1 inch wide by 0.060 inch thick. Thespring material can be lnconel X 750, L5 inches at the widest part ofthe trapezoid and 0.5 inch at the narrow end.

Thus, it will be seen that there is here provided atemperature-compensating mask-mounting system with many advantages overthe prior art. It is simple and inexpensive to manufacture and requiresno changes or modification to be made to the existing mask-framestructure.

While there have been shown and described what are at present consideredthe preferred embodiments of the invention, it will be obviousto thoseskilled in the art that various changes and modifications may be madetherein without departing from the scope of the invention as defined bythe appended claims.

lclaim:

l. A color cathode-ray tube containing, within an evacuated envelope, amosaic cathodoluminescent screen, an electron source positioned remotefrom said screen, and a parallax barrier mounted between said source andsaid screen but closer to said screen, said parallax barrier having aforaminated relatively fragile portion attached at its peripheral edgeto one end of a circumferential sidewall of a relatively rigid frame,said circumferential sidewall extending substantially perpendicular tosaid screen and having an inwardly projecting flange substantiallyparallel to said screen formed on the end of said wall remote from saidforaminous portion, and means for releasably mounting said barrierwithin said tube, said means comprising: a plurality of flat metallicelements positioned at spaced intervals about said frame and attached tosaid flange, each of said elements having a depending spring attachedthereto and extending toward said screen between said circumferentialwall of said frame and said envelope and having means formed thereinengaging mating means formed on said envelope, said flat metallicelements being composed of two contiguous layers of material, one ofwhich has a higher coefficient of thermal expansion than the other, andsaid higher coefficient material being adjacent said flange.

2. The invention of claim 1 wherein said flat metallic elements aresubstantially rectangular having a long side and a short side and saidlong side extends approximately parallel to said flange.

3. The invention of claim 1 wherein said flat metallic elements are fourin number and said spaced intervals are approximately apart, and each ofsaid elements is attached to said flange by a plurality of attachmentmeans, each of said attachment means being spaced inwardly from the backedge of said elements a substantially equal distance.

4. The invention of claim I wherein said flat metallic elements arethree in number, a first one of said elements being positionedsubstantially on the vertical axis of said flange and a second and thirdof said elements being oppositely disposed on said flange and beingpositioned below the horizontal axis of said flange, each of saidelements being attached to said flange by a plurality of attachmentmeans, the attachment means on said first element being spaced inwardlyfrom the back edge of said first element a substantially equal distanceand the attachment means on said second and third elements being spacedprogressively further from the back edge of the elements as the distancefrom said horizontal axis increases.

5. The invention of claim 1 wherein said depending spring issubstantially trapezoidal in configuration.

1. A color cathode-ray tube containing, within an evacuated envelope, amosaic cathodoluminescent screen, an electron source positioned remotefrom said screen, and a parallax barrier mounted between said source andsaid screen but closer to said screen, said parallax barrier having aforaminated relatively fragile portion attached at its peripheral edgeto one end of a circumferential sidewall of a relatively rigid frame,said circumferential sidewall extending substantially perpendicular tosaid screen and having an inwardly projecting flange substantiallyparallel to said screen formed on the end of said wall remote from saidforaminous portion, and means for releasably mounting said barrierwithin said tube, said means comprising: a plurality of flat metallicelements positioned at spaced intervals about said frame and attached tosaid flange, each of said elements having a depending spring attachedthereto and extending toward said screen between said circumferentialwall of said frame and said envelope and having means formed thereinengaging mating means formed on said envelope, said flat metallicelements being composed of two contiguous layers of material, one ofwhich has a higher coefficient of thermal expansion than the other, andsaid higher coefficient material being adjacent said flange.
 2. Theinvention of claim 1 wherein said flat metallic elements aresubstantially rectangular having a long side and a short side and saidlong side extends approximately parallel to said flange.
 3. Theinvention of claim 1 wherein said flat metallic elements are four innumber and said spaced intervals are approximately 90* apart, and eachof said elements is attached to said flange by a plurality of attachmentmeans, each of said attachment means being spaced inwardly from the backedge of said elements a substantially equal distance.
 4. The inventionof claim 1 wherein said flat metallic elements are three in number, afirst one of said elements being positioned substantially on thevertical axis of said flange and a second and third of said elementsbeing oppositely disposed on said flange and being positioned below thehorizontal axis of said flange, each of said elements being attached tosaid flange by a plurality of attachment means, the attachment means onsaid first element being spaced inwardly from the back edge of saidfirst element a substantially equal distance and the attachment means onsaid second and third elements being spaced progressively further fromthe back edge of the elements as the distance from said horizontal axisincreases.
 5. The invention of claim 1 wherein said depending spring issubstantially trapezoidal in configuration.